Grinding mill



Sept. 17, 1935.

J. P. WALEs w GRINDING MI'LL Jv P. WALES GRINDING MILL Sept. 17, 1935.

Filed Oct. 20, 2 Sheets-Sheet 2 FIG. 5

TOR' w fMLd/zl vL ATToRNEYs.

Patentecl Sept. 17, 1935 UNITED' STATES PATENT oFFlcE A Mine and Smelter Supply Colo.

Company, Denver,

Application October 20, 1 931, Serial No. 569,913 i 4 Claims.

My invention'relates to cylindrical grinding mill's. An important object of the invention is to construct a cylindrical grinding mill that may be operated at a higher speed than heretofore possibIe.

In this art, it has been thought necessary to run a mill at less than the critical speed. The "criticalspeed Vis that Velocity of rotation that will cause the outer layer of grinding media to cling to the inner surface of the mill throughout rotation, by reason of centrifugal force. Of course, it is necessary 'that the grinding medium (balls, rods or pebbles) descend; i. e., fall or roll, toward the bottom of the mill during rotation, in order to grind material in the mill. If the grinding media cling to the inner wall of the mill throughout lrotation thereof, no grinding takes place.

However, the fasterthat the shell is rotated, the higher it raises the grinding medium, the greater the impact, providing the grinding medium rolls or falls to the bottom, and the greater the kinetic .energy |of the grinding charge.

-An object of the invention, therefore, is to nbtain greater efiiciency by rotating my mill at va Velocity greater than the critical speed and yet prevent grinding media from c'linging to the shell, as stated.

Another object isV to eliminate the so-called dead spot in a grinding mill, which is the re- 'gion in a grinding mill about which the grindi-ng medium revolves, and in which region little 'or no grinding takes place.

A further `object of the'invention is to provide means to divert the grinding medium and material revolving at high speed, from any position around the inner surface of the mill toward the bottom, thus making available this increased energy for impact on the material and pgrinding ;media in the lower part of the mill.

Still another object is to eliminate lifters for the 'grinding medium and for the ground material.

lOther objects reside in details of construction of parts and in novel combinations and arrangements of parts, which will appear in the course of the following description. In the drawings, like reference characters designate similar parts in the several views.

Figure 1 is a longitudinal, Vertical sectional view of an embodiment of my invention.

Figure 2 is a section taken on the line 2-2, looking in the direction of the arrows.

Figures 3 and V4 are perspective Views of different constructions of baiiles or scrapers com- .prised in the invention.

Figures 5 and 6 are cross Sections taken on the line 5-5 of Figure 1, looking in Athe direction of z the arrows, showing the baille or scraper in several positions.

Referring more in detail to the drawings, the reference characters 1, 8 and 9 designate base members or supports upon which a grinding mill w is mounted. Bases 8 and 9 respectively support bearings'll and 12 for trunnions l3 and 14 of the mill. The top of the bearings have oil caps The mill has a conventional ring gear IB for .driving same, and a dipper ll for feeding material to the inlet trunnion |3. Helically arranged ribs 54 in the latter trunnion feed material into the shell '18, by rotation of the mill. The direction of rotation of the mill is shown by the arrow A" in Figures 2, 5 and 6. The mill has a sectional lining IS held in place by bolts 2D. The bolts hold Sections 30, whose edges converge to- Ward the shell. Between these .Sections are other dove-tai'l Sections 3|, whose edges .diverge toward the shell, as shown in Figures 5 and 6.

Head 2| at the feed end of the mill has a lining 22 provided with a beveled central opening 23 for the inlet'of feed material. Head 24 at the discharge end of the mill supports the ring gear |6.

The Vshell and heads have abutting flanges 25 for fastening said elements together. Spaced from the mill end 24 is 'an internally projecting i rim 26. A grid 21 of usual form is disposed within the mill against the rim 26, divides the she'll into a grinding chamber 55 and a discharge space 2B. The grid is arranged between the rim 26 and .the end of the lining Sections I9 of the shell.

A bafiie or scraper 29 is provided within the mill. Figures 3 and 4 show different constructions of the baflle and Figures 5 and 6 show differentA arrangements of same within the shell. The bafile comprises a curved back member 32 and bracing members 33 conforming with the curved interior of the back member. The members 33 are spaced inward from the ends of the curved member, as indicated at 34. This space is large enough for a ball to enter without wenging. If this space were not provided, as the head liner and grid wore away from the braces, at a certain point the balls would wedge therebetween. Wedging is avoided by my arrangement.

As shown in Figures 3 and 4, the edges of the curved back member 32 may be non-parallel, as

by cutting either the front edge 35 or the rear edge 36 at a bias.

In the space 28, a relatively stationary scoop 31 is -arranged with its lip 38 adjacent the inner surface of the space. By this means, ground material that is fine enough to pass through the grid, is scooped off of the circumferential wall of the space 28, and the material falls into a trough 39 at the bottom of the sc'oop 31. Were this scoop not used, the pulverized material would adhere to the wall of this space, on account of the rapid rotation of the mill. From the trough 39, the material runs out of the mill through the pipe 40.

The scoop 31 is supported on a standard 4| on the base 9. Wedge blocks 42 between the base and the standard are used to adjust the scoop in a Vertical plane. The pipe 40 and its associated scoop 31 may be rotated relative to the standard, to adjust the scoop in a rotary path, relative to the shell Wall.

The baflle 29 is supported at one side on a shaft 43, by being bolted to a vflange 44 on the shaft. The other side of the bafile is supported by telesooping members 44 and 45 on the scoop 31 and on the baiile respectively. The telescoping member 44 is shown as being integral with the scoop and the member 45 is shown as being bolted to the bafile through the medium of a flange 46 on the member 45.

To effect rotary adjustment of the bafile 29, as shown in full and dotted lines in Figures and 6, the shaft 43 is rotated by a worm gear 41 controlled by a`worm 48 on a shaft 49. The shaft 43 is supported on a standard 50 on the base 1. Wedge blocks 5| beneath the standard are utilized for Vertical adjustment of the shaft 43.

In the operation of the mill, it is no doubt clear that the direction of movement of the balls, or other grinding medium, is Controlled by the bias cut of the edges of the curved back member. Moreover, it is thought clear without further illustration, that the back member of the baflie may be of any other plain, geometrical shape, such as a square, rectangle, parallelogram, right angle triangle, etc., and may be flat, conc-ave, convex, a l-ogarithmic spiral (as shown in the .drawings) a parabola, a hyperbola, etc. in section.

Lip 52 of the bafiie is preferably near the inner periphery of the mill Shell. As can be seen, it is desirable th-at the space between this lip `and the shell liner be less than the diameter of the grinding medium (balls, for instance) even at the point of greatest wear of the shell lner sections. Thus wedging of the balls between the lip and the liner sections can be avoided. The lip 52 is preferably beveled, as shown in Figures 5 and 6.

The position of the bafile and scoop 31, or either of them, may be changed as desired. The position of the bafile is altered in a rotary path by the worm 49 and worm gear 41. Due to the pivotal support for the baflle by the telescoping members 44 and 45, the baffle may be adjusted relative to the scoop 31. The scoop is rotated by turning the conduit 40. The height of the scoop 31 and the shaft 43 is regulated by the number and position of the wedge blocks 42 and 5|.

The mill during operation is rotated at greater than the Critical speed, and as the balls, or other medium, and material strike the bafiie, they are 5 diverted at high speed from the centrifugal path by means of the baffie, and are forced to impinge on the material and other balls or medium below. The scoop 31 scrapes ofi the pulverized material that has passed through the grid and is clinging to the inner surface of the space 28 on account of the comparatively rapid 'rotation of the mill.

The feed material is lifted up by the dipper |1, travels through the trunnion |3 by reason of the spiral ribs 54, and is discharged through the trough 39 and conduit 49 after grinding.

A distinct advantage of the present mill is the fact that the active, working volume is greater than heretofore attained.

It is to be understood that changes may be made in the details of construction and in the combination and arrangement of parts without departing from the broad principle or the spirit and scope of the invention.

What I claim and desire to secure by Letters Patent is:

1. A grinding mill comprising a rotary shell having inlet and discharge openings, a grid in the shell, separating same into grinding and discharge chambers, a stationar'y baffle in the grinding 30.

chamber, a scoop in the discharge chamber, and supports for the baflie and for the scoop extending through the inlet and discharge openings, the scoop and bafile being pivotally connected through the grid.

2. A grinding mill according to claim 1, in which telescoping members on the scoop and baffle al'ford the pivotal connection.

3. A grinding mill comprising a rotary drum having an inlet and an outlet at opposite ends,

a defiective bale having a cutting edge contigu- |ous to the inner circumferential surface of the drum, to interrupt the rotary movement of material congregated against said surface under the influence of centrifugal force, a grid spaced from l the outlet end of the drum to provide a chamber for the product of the grinding action, and a scoop in said chamber to remove the product from under the influence of centrifugal force for its movev ment to and through the outlet. 4. A grinding mill comprising a rotary ldrum having an inlet and an outlet at opposite ends,

a deflective baffle having a cutting edge contiguous to the inner circumferential surface of the drum, to interrupt the rotary movement of ma- 5h5` terial congregated against said surface under the influence of centrifugal force, a grid spaced from the outlet end of the drum to provide a chamber for the product of the grinding action, and a stationary scoop in said chamber to remove the product from under the influence of centrifugal force, having a discharge con-duit in the outlet.

JESS P. WALES. 

